1. Field of the Invention
This invention relates generally to teaching systems, for example, as in so-called language laboratories, and more particularly is directed to improvements in the transmission of various signals between a master or central station at which a proctor or supervisor of the teaching system may be situated, and one or more student stations remote from the master station.
2. Description of the Prior Art
In most existing teaching systems, for example, as are used in language laboratories, numerous electrical cables extend between a master station and one or more student stations for the exchange therethrough of various signals, such as, the main signals representing teaching or instructional materials played from tapes or other records at the master station, audio signals for communication between the proctor or supervisor and the various students, control signals for controlling, from the master station, devices situated at the student stations, such as the tape or other record players for recording and/or reproducing the main signals and/or audio signals from the students, and answer-representing signals transmitted from the various student stations to the master station for evaluation or scoring thereat. In the existing teaching systems, as aforesaid, the numerous cables required for exchanging the signals between the master and student stations are expensive to install, and substantially prevent the transportation from one locale to another of the equipment comprising the teaching system. Accordingly, as a practical matter, the existing teaching systems are permanent installations which, therefore, are available for use only in rather restricted areas.
In view of the foregoing, it has been suggested to effect radio or wireless transmission of the signals that need to be exchanged between the master and student stations of teaching systems as such mode of transmission, even though it requires transmitters and receivers, is less costly than the conventional arrangement employing cables and, furthermore, permits the teaching system to be conveniently transported and easily set up for use at various sites. However, problems arise in the radio or wireless transmission of signals in teaching systems by reason of the relatively large number of different types of signals that need to be transmitted, particularly from the master station to each student station. As previously mentioned, in the case of a teaching system to be used as a language laboratory, the signals which need to be transmitted from the master station to each student station may include at least main signals such as may be reproduced by a tape or other record player from a recorded master tape, audio signals for communication between the proctor, supervisor or teacher and the students, and control signals for remotely controlling from the master station devices, such as the above-noted tape or other record players, situated at the student stations. When wireless or radio transmission is employed for the foregoing different types of signals, different frequency bands are assigned to the several types of signals, respectively, so that it is necessary to provide each student station with a corresponding number of receivers tuned to the different transmitting frequencies. Accordingly, existing teaching systems employing radio or wireless signal transmission are complex and relatively costly, and do not provide wholly reliable operation.